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From "Runping Qi (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-156) Reducer threw IOEOFException
Date Thu, 20 Apr 2006 21:11:05 GMT
Reducer  threw IOEOFException
-----------------------------

         Key: HADOOP-156
         URL: http://issues.apache.org/jira/browse/HADOOP-156
     Project: Hadoop
        Type: Bug

    Reporter: Runping Qi



A job was running with all the map tasks completed.
The reducers were appending the intermediate files into the large intermediate file.
java.io.EOFException was thrown when the record reader tried to read the version number
during initialization. Here is the stack trace:

java.io.EOFException 
    at java.io.DataInputStream.readFully(DataInputStream.java:178) 
    at java.io.DataInputStream.readFully(DataInputStream.java:152) 
    at org.apache.hadoop.io.SequenceFile$Reader.init(SequenceFile.java:251) 
    at org.apache.hadoop.io.SequenceFile$Reader.(SequenceFile.java:236) 
    at org.apache.hadoop.io.SequenceFile$Reader.(SequenceFile.java:226) 
    at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:205) 
    at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:709) 

Appearantly, the intermediate file was empty. I suspect that one map task
generated empty intermidiate files for all the reducers, since all the reducers
failed at the same place, and failed at the same place during retries.

Unfortunately, we cannot know which map task generated the empty files,
since the exception does not offer any clue.

One simple enhancement is that the record reader should catch IOException and re-throw it
with additional 
information, such as the file name.



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